Effect of shoe modifications on center of pressure and in-shoe plantar pressures

This study was conducted to determine the effect of footwear modification on patients with neuromusculoskeletal disorders. Two analyses, the center of pressure and the in-shoe plantar pressures, were studied with the help of healthy volunteers so that the effect of shoe modifications could be assessed. The ground force under the sole of the shoe was measured while the subjects were walking, and the plantar pressure at the foot-insole interface and its distribution were measured while the subjects were in both the standing and walking positions, wearing the trial shoes. The trial shoes had three different types of heels-standard heel, Thomas heel, and reverse Thomas heel-and had three different locations for the rocker bar--just under the metatarsophalangeal joint, 1 cm behind the metatarsophalangeal joint, and 1 cm before the metatarsophalangeal joint. The shift change at the center of pressure showed that the Thomas heel generally pushed the center of pressure more laterally and the reverse Thomas heel shifted it medially more than the standard heel did. While the subjects were in a stable standing position wearing the Thomas heel shoes, the medial forefoot and the lateral heel region's pressure showed significant reduction in the plantar pressure and the lateral forefoot and the medial heel showed a tendency to rise, compared with the standard heel condition. When the trial shoes' heels were changed to the reverse Thomas heel, the above changes tended to reverse. Tests at the foot-insole interface showed that the different types of heels and the location of the bar could change not only the pressure distribution but also the duration of the plantar pressure under the lateral area that shifted to the medial area when the subjects walked. This pressure measurement method was very useful for the design and evaluation of such footwear.